This description relates to loading ramps, and more particularly to actuating mechanisms for raising and lowering a loading ramp on a trailer or truck.
Large or heavy equipment or other cargo can be transported using a trailer connected to a vehicle or a truck. For example, flatbed-type trailers commonly include a hitch assembly (e.g., a gooseneck) that connects to a truck or tractor, such that the truck or tractor can pull the trailer and its cargo. A flatbed truck can similarly facilitate transportation of large or heavy cargo.
It is often desirable to load the cargo onto the trailer or truck without having to lift the cargo directly onto a top surface of the trailer or truck. For example, automobiles, construction or farm equipment, all-terrain vehicles, or other wheeled vehicles can be more conveniently loaded onto the top surface by rolling the vehicles or equipment onto the trailer or truck. Mechanisms exist that allow for loading of cargo onto a trailer without lifting the cargo. For example, ramps that are connected to an end of a trailer by a hinge can allow the ramps to be flipped over onto the bed of the trailer for transport. Tilt trailers that allow the entire bed of the trailer to tilt so that wheeled vehicles can be rolled onto the trailer similarly facilitate loading of cargo. Such ramps are often very heavy and, as a result, are difficult or impossible for a single user to move the ramp between the open and closed positions.
Flatbed-type trailers have also been developed with a rear end that includes a dovetail portion that is connected to a main portion of the trailer by a hinge that allows the dovetail portion to rotate relative to the main portion. This type of dovetail is generally designed to move between a generally horizontal transport position (i.e., where the dovetail is substantially co-planar with the main flatbed portion of the trailer), and a downwardly-oriented position for loading and unloading (i.e., where the dovetail is positioned at an angle with respect to the main portion of the trailer) such that the dovetail acts as a ramp between the ground and the main flatbed portion of the trailer. When the dovetail is in the downwardly-oriented position, cargo, particularly wheeled cargo, can be more easily loaded onto and unloaded from the trailer. After loading and unloading, the dovetail can be moved to the transport position so that the dovetail has sufficient ground clearance.
While trailers with dovetails facilitate loading and unloading cargo, the size and weight of the dovetails make them difficult to move between the load and transport positions. Many such dovetail trailers use hydraulic systems to actuate the dovetails. Such systems are prone to failure and therefore generally need to include a secondary locking mechanism for securing the dovetail in at least the transport position. The locking mechanism increases the complexity of the system, making it more complicated to operate and more prone to user error or inconvenience. Even with a locking mechanism, the hydraulic cylinders are generally fully or mostly extended for transport (i.e., to hold the dovetail in the upper, transport position), which places a great deal of strain on the hydraulic cylinders because they are supporting the weight of the dovetail. This strain reduces the lifetime of the cylinders and can increase the chances of failure at highly inconvenient times. Furthermore, such dovetail trailers generally have a relatively low hauling weight capacity on the dovetail portion of the trailer. As a result, cargo often must be loaded forward of the dovetail, so that a longer overall trailer is required and/or so that the dovetail is less useful for transport.